This invention relates to compounds useful as neuroprotectants, anticonvulsants, anxiolytics, analgesics, muscle relaxants or adjuvants to general anesthetics. The invention relates as well to methods useful for the treatment of neurological disorders and diseases, including, but not limited to, global and focal ischemic and hemorrhagic stroke, head trauma, spinal cord injury, hypoxia-induced nerve cell damage such as in cardiac arrest or neonatal distress, epilepsy, anxiety, and neurodegenerative diseases such as Alzheimer""s Disease, Huntington""s Disease, Parkinson""s Disease, and amyotrophic lateral sclerosis (ALS). The invention relates as well to methods of screening for compounds active at a novel site on receptor-operated calcium channels, and thereby possessing therapeutic utility as neuroprotectants, anticonvulsants, anxiolytics, analgesics, muscle relaxants or adjuvants to general anesthetics, and/or possessing potential therapeutic utility for the treatment of neurological disorders and diseases as described above.
The following is a description of relevant art, none of which is admitted to be prior art to the claims.
Glutamate is the major excitatory neurotransmitter in the mammalian brain. Glutamate binds or interacts with one or more glutamate receptors which can be differentiated pharmacologically into several subtypes. In the mammalian central nervous system (CNS) there are three main subtypes of ionotropic glutamate receptors, defined pharmacologically by the selective agonists N-methyl-D-aspartate (NMDA), kainate (KA), and xcex1-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). The NMDA receptor has been implicated in a variety of neurological pathologies including stroke, head trauma, spinal cord injury, epilepsy, anxiety, and neurodegenerative diseases such as Alzheimer""s Disease (Watkins and Collingridge, The NMDA Receptor, Oxford: IRL Press, 1989). A role for NMDA receptors in nociception and analgesia has been postulated as well (Dickenson, A cure for wind-up: NMDA receptor antagonists as potential analgesics. Trends Pharmacol. Sci. 11: 307, 1990). More recently, AMPA receptors have been widely studied for their possible contributions to such neurological pathologies (Fisher and Bogousslavsky, Evolving toward effective therapy for acute ischemic stroke. J. Amer. Med. Assoc. 270: 360, 1993; Yamaguchi et al., Anticonvulsant activity of AMPA/kainate antagonists: Comparison of GYKI 52466 and NBQX in maximal electroshock and chemoconvulsant seizure models. Epilepsy Res. 15: 179, 1993).
When activated by glutamate, the endogenous neurotransmitter, the NMDA receptor permits the influx of extracellular calcium (Ca2+) and sodium (Na+) through an associated ion channel. The NMDA receptor allows considerably more influx of Ca2+ than do kainate or AMPA receptors (but see below), and is an example of a receptor-operated Ca2+ channel. Normally, the channel is opened only briefly, allowing a localized and transient increase in the concentration of intracellular Ca2+ ([Ca2+]i), which, in turn, alters the functional activity of the cell. However, prolonged increases in [Ca2+]i, resulting from chronic stimulation of the NMDA receptor, are toxic to the cell and lead to cell death. The chronic elevation in [Ca2+]i, resulting from stimulation of NMDA receptors, is said to be a primary cause of neuronal degeneration following a stroke (Choi, Glutamate neurotoxicity and diseases of the nervous system. Neuron 1: 623, 1988). Overstimulation of NMDA receptors is also said to be involved in the pathogenesis of some forms of epilepsy (Dingledine et al., Excitatory amino acid receptors in epilepsy. Trends Pharmacol. Sci. 11: 334, 1990), anxiety (Wiley and Salster, Preclinical evaluation of N-methyl-D-aspartate antagonists for antianxiety effects: A review. In: Multiple Sigma and PCP Receptor Ligands: Mechanisms for Neuromodulation and Neuroprotection? NPP Books, Ann Arbor, Mich., pp. 801-815, 1992), neurodegenerative diseases (Meldrum and Garthwaite, Excitatory amino acid neurotoxicity and neurodegenerative disease. Trends Pharmacol. Sci. 11: 379, 1990), and hyperalgesic states (Dickenson, A cure for wind-up: NMDA receptor antagonists as potential analgesics. Trends Pharmacol. Sci. 11: 307, 1990).
The activity of the NMDA receptor-ionophore complex is regulated by a variety of modulatory sites that can be targeted by selective antagonists. Competitive antagonists, such as the phosphonate APB, act at the glutamate binding site, whereas noncompetitive antagonists, such as phencyclidine (PCP), MK-801 or magnesium (Mg2+), act within the associated ion channel (ionophore). There is also a glycine binding site that can be blocked selectively with compounds such as 7-chlorokynurenic acid. There is evidence suggesting that glycine acts as a co-agonist, so that both glutamate and glycine are necessary to fully elicit NMDA receptor-mediated responses. Other potential sites for modulation of NMDA receptor function include a zinc (Zn2+) binding sit and a sigma ligand binding site. Additionally, endogenous polyamines such as spermine are believed to bind to a specific site and so potentiate NMDA receptor function (Ransom and Stec, Cooperative modulation of [3H]MK-801 binding to the NMDA receptor-ion channel complex by glutamate, glycine and polyamines. J. Neurochem. 51: 830, 1988). The potentiating effect of polyamines on NMDA receptor function may be mediated via a specific receptor site for polyamines; polyamines demonstrating agonist, antagonist, and inverse agonist activity have been described (Reynolds, Arcaine is a competitive antagonist of the polyamine site on the NMDA receptor. Europ. J. Pharmacol. 177: 215, 1990; Williams et al., Characterization of polyamines having agonist, antagonist, and inverse agonist effects at the polyamine recognition site of the NMDA receptor. Neuron 5: 199, 1990). Radioligand binding studies have demonstrated additionally that higher concentrations of polyamines inhibit NMDA receptor function (Reynolds and Miller, Ifenprodil is a novel type of NMDA receptor antagonist: Interaction with polyamines. Molec. Pharmacol. 36: 758, 1989; Williams et al., Effects of polyamines on the binding of [3H]MK-801 to the NMDA receptor: Pharmacological evidence for the existence of a polyamine recognition site. Molec. Pharmacol. 36: 575, 1989; Sacaan and Johnson, Characterization of the stimulatory and inhibitory effects of polyamines on [3H]TCP binding to the NMDA receptor-ionophore complex. Molec. Pharmacol. 37: 572, 1990). This inhibitory effect of polyamines on NMDA receptors is probably a nonspecific effect (i.e., not mediated via the polyamine receptor) because patch clamp electro-physiological studies have demonstrated that this inhibition is produced by compounds previously shown to act at the polyamine receptor as either agonists or antagonists (Donevan et al., Arcaine Blocks N-Methyl-D-Aspartate Receptor Responses by an Open Channel Mechanism: Whole-Cell and Single-Channel Recording Studies in Cultured Hippocampal Neurons. Molec. Pharmacol. 41: 727, 1992; Rock and Macdonald, Spermine and Related Polyamines Produce a Voltage-Dependent Reduction of NMDA Receptor Single-Channel Conductance. Molec. Pharmacol. 42: 157, 1992).
Recent studies have demonstrated the molecular diversity of glutamate receptors (reviewed by Nakanishi, Molecular Diversity of Glutamate Receptors and Implications for Brain Function. Science 258: 597, 1992). At least five distinct NMDA receptor subunits (NMDAR1 and NMDAR2A through NMDAR2D), each encoded by a distinct gene, have been identified to date. Also, in NMDAR1, alternative splicing gives rise to at least six additional isoforms. It appears that NMDAR1 is a necessary subunit, and that combination of NMDAR1 with different members of NMDAR2 forms the fully functional NMDA receptor-ionophore complex. The NMDA receptor-ionophore complex, thus, can be defined as a hetero-oligomeric structure composed of at least NMDAR1 and NMDAR2 subunits; the existence of additional, as yet undiscovered, subunits is not excluded by this definition. NMDAR1 has been shown to possess binding sites for glutamate, glycine, Mg2+, MK-801, and Zn2+. The binding sites for sigma ligands and polyamines have not yet been localized on NMDA receptor subunits, although ifenprodil recently has been reported to be more potent at the NMDAR2B subunit than at the NMDAR2A subunit (Williams, Ifenprodil discriminates subtypes of the N-methyl-D-aspartate receptor: selectivity and mechanisms at recombinant heteromeric receptors. Mol. Pharmacol. 44: 851, 1993).
Several distinct subtypes of AMPA and kainate receptors have been cloned as well (reviewed by Nakanishi, Molecular diversity of glutamate receptors and implications for brain function. Science 258: 597, 1992). Of particular relevance are the AMPA receptors designated GluR1, GluR2, GluR3, and GluR4 (also termed GluRA through GluRD), each of which exists in one of two forms, termed flip and flop, which arise by RNA alternative splicing. GluR1, GluR3 and GluR4, when expressed as homomeric or heteromeric receptors, are permeable to Ca2+, and are therefore examples of receptor-operated Ca2+ channels. Expression of GluR2 alone or in combination with the other subunits gives rise to a receptor which is largely impermeable to Ca2+. As most native AMPA receptors studied in situ are not Ca2+-permeable (discussed above), it is believed that such receptors in situ possess at least one GluR2 subunit.
Furthermore, it is hypothesized that the GluR2 subunit is functionally distinct by virtue of the fact that it contains an arginine residue within the putative pore-forming transmembrane region II; GluR1, GluR3 and GluR4 all contain a glutamine residue in this critical region (termed the Q/R site, where Q and R are the single letter designations for glutamine and arginine, respectively). The activity of the AMPA receptor is regulated by a number of modulatory sites that can be targeted by selective antagonists (Honore et al., Quinoxalinediones: potent competitive non-NMDA glutamate receptor antagonists. Science 241: 701, 1988; Donevan and Rogawski, GYKI 52466, a 2,3-benzodiazepine, is a highly selective, noncompetitive antagonist of AMPA/kainate receptor responses. Neuron 10: 51, 1993). Competitive antagonists such as NBQX act at the glutamate binding site, whereas compounds such as GYKI 52466 appear to act noncompetitively at an associated allosteric site.
Compounds that act as competitive or noncompetitive antagonists at the NMDA receptor are said to be effective in preventing neuronal cell death in various in vitro neurotoxicity assays (Meldrum and Garthwaite, Excitatory amino acid neurotoxicity and neurodegenerative disease. Trends Pharmacol. Sci. 11: 379, 1990) and in in vivo models of stroke (Scatton, Therapeutic potential of NMDA receptor antagonists in ischemic cerebrovascular disease in Drug Strategies in the Prevention and Treatment of Stroke, IBC Technical Services Ltd., 1990). Such compounds are also effective anticonvulsants (Meldrum, Excitatory amino acid neurotransmission in epilepsy and anticonvulsant therapy in Excitatory Amino Acids. Meldrum, Moroni, Simon, and Woods (Eds.), New York: Raven Press, p. 655, 1991), anxiolytics (Wiley and Balster, Preclinical evaluation of N-methyl-D-aspartate antagonists for antianxiety effects: A review. In: Multiple Sigma and PCP Receptor Ligands: Mechanisms for Neuromodulation and Neuroprotection? NPP Books, Ann Arbor, Mich., pp. 801-815, 1992), and analgesics (Dickenson, A cure for wind-up: NMDA receptor antagonists as potential analgesics. Trends Pharmacol. Sci. 11: 307, 1990), and certain NMDA receptor antagonists may lessen dementia associated with Alzheimer""s Disease (Hughes, Merz"" novel approach to the treatment of dementia. Script No. 1666: 24, 1991).
Similarly, AMPA receptor antagonists have come under intense scrutiny as potential therapeutic agents for the treatment of such neurological disorders and diseases. AMPA receptor antagonists have been shown to possess neuroprotectant (Fisher and Bogousslavsky, Evolving toward effective therapy for acute ischemic stroke. J. Amer. Med. Assoc. 270: 360, 1993) and anticonvulsant (Yamaguchi et al., Anticonvulsant activity of AMPA/kainate antagonists: comparison of GYKI 52466 and NBQX in maximal electroshock and chemoconvulsant seizure models. Epilepsy Res. 15: 179, 1993) activity in animal models of ischemic stroke and epilepsy, respectively.
The nicotinic cholinergic receptor present in the mammalian CNS is another example of a receptor-operated Ca2+ channel (Deneris et al., Pharmacological and functional diversity of neuronal nicotinic acetylcholine receptors. Trends Pharmacol. Sci. 12: 34, 1991). Several distinct receptor subunits have been cloned, and these subunits can be expressed, in Xenopus oocytes for example, to form functional receptors with their associated cation channels. It is hypothesized that such receptor-ionophore complexes are heteropentameric structures. The possible role of nicotinic receptor-operated Ca2+ channels in the pathology of neurological disorders and diseases such as ischemic stroke, epilepsy and neurodegenerative diseases has been largely unexplored.
It has been demonstrated previously that certain spider and wasp venoms contain arylalkylamine toxins (also called polyamine toxins, arylamine toxins, acylpolyamine toxins or polyamine amide toxins) with activity against glutamate receptors in the mammalian CNS (for reviews see Jackson and Usherwood, Spider toxins as tools for dissecting elements of excitatory amino acid transmission. Trends Neurosci. 11: 278, 1988; Jackson and Parks, Spider Toxins: Recent Applications In Neurobiology. Annu. Rev. Neurosci. 12: 405, 1989; Saccomano et al., Polyamine spider toxins: Unique pharmacological tools. Annu. Rep. Med. Chem. 24: 287, 1989; Usherwood and Blagbrough, Spider Toxins Affecting Glutamate Receptors: Polyamines in Therapeutic Neurochemistry. Pharmacol. Therap. 52: 245, 1991; Kawai, Neuroactive Toxins of Spider Venoms. J. Toxicol. Toxin Rev. 10: 131, 1991). Arylalkylamine toxins were initially reported to be selective antagonists of the AMPA/kainate subtypes of glutamate receptors in the mammalian CNS (Kawai et al., Effect of a spider toxin on glutaminergic synapses in the mammalian brain. Biomed. Res. 3: 353, 1982; Saito et al., Spider Toxin (JSTX) blocks glutamate synapse in hippocampal pyramidal neurons. Brain Res. 346: 397, 1985; Saito et al., Effects of a spider toxin (JSTX) on hippocampal CA1 neurons in vitro. Brain Res. 481: 16, 1989; Akaike et al., Spider toxin blocks excitatory amino acid responses in isolated hippocampal pyramidal neurons. Neurosci. Lett. 79: 326, 1987; Ashe et al., Argiotoxin-636 blocks excitatory synaptic transmission in rat hippocampal CA1 pyramidal neurons. Brain Res. 480: 234, 1989; Jones et al., Philanthotoxin blocks quisqualate-induced, AMPA-induced and kainate-induced, but not NMDA-induced excitation of rat brainstem neurones in vivo. Br. J. Pharmacol. 101: 968, 1990). Subsequent studies have demonstrated that while certain arylalkylamine toxins are both nonpotent and nonselective at various glutamate receptors, other arylalkylamines are both very potent and selective at antagonizing responses mediated by NMDA receptor activation in the mammalian CNS (Mueller et al., Effects of polyamine spider toxins on NMDA is receptor-mediated transmission in rat hippocampus in vitro. Soc. Neurosci. Abst. 15: 945, 1989; Mueller et al., Arylamine spider toxins antagonize NMDA receptor-mediated synaptic transmission in rat hippocampal slices. Synapse 9: 244, 1991; Parks et al., Polyamine spider toxins block NMDA receptor-mediated increases in cytosolic calcium in cerebellar granule neurons. Soc. Neurosci. Abst. 15: 1169, 1989; Parks et al., Arylamine toxins from funnel-web spider (Agelenopsis aperta) venom antagonize N-methyl-D-aspartate receptor function in mammalian brain. J. Biol. Chem. 266: 21523, 1991; Priestley et al., Antagonism of responses to excitatory amino acids on rat cortical neurones by the spider toxin, argiotoxin-636. Br. J. Pharmacol. 97: 1315, 1989; Draguhn et al., Argiotoxin-636 inhibits NMDA-activated ion channels expressed in Xenopus oocytes. Neurosci. Lett. 132: 187, 1991; Kiskin et al., A highly potent and selective N-methyl-D-aspartate receptor antagonist from the venom of the Agelenopsis aperta spider. Neuroscience 51: 11, 1992; Brackley et al., Selective antagonism of native and cloned kainate and NMDA receptors by polyamine-containing toxins. J. Pharmacol. Exptl. Therap. 266: 1573, 1993; Williams, Effects of Agelenopsis aperta toxins on the N-methyl-D-aspartate receptor: Polyamine-like and high-affinity antagonist actions. J. Pharmacol. Exptl. Therap. 266: 231, 1993). Inhibition of nicotinic cholinergic receptors by the arylalkylamine toxin philanthotoxin has also been reported (Rozental et al., Allosteric inhibition of nicotinic acetylcholine receptors of vertebrates and insects by philanthotoxin. J. Pharmacol. Exptl. Therap. 249: 123, 1989).
Parks et al. (Arylamine toxins from funnel-web spider (Agelenopsis aperta)venom antagonize N-methyl-D-aspartate receptor function in mammalian brain. S. Biol. Chem. 266: 21523, 1991), describe arylalkylamine spider toxins (xcex1-agatoxins) which antagonize NMDA receptor function in mammalian brain. The authors discuss the mechanism of action of arylalkylamine toxins, and indicate that an NMDA receptor-operated ion channel is the probable site of action of the xcex1-agatoxins, and most probably other spider venom arylalkylamines. They state:
The discovery that endogenous polyamines in the vertebrate brain modulate the function of NMDA receptors suggests that the arylamine toxins may produce their antagonism via a polyamine-binding site on glutamate receptors. Brackley et al. studied the effects of spermine and philanthotoxin 433 on the responses evoked by application of excitatory amino acids in Xenopus oocytes injected with mRNA from rat or chick brain. These authors reported that, at concentrations below those that antagonize glutamate receptor function, both spermine and philanthotoxin potentiate the effects of excitatory amino acids and some other neurotransmitters. On the basis of these and other data, Brackley et al. concluded that the arylamine toxins may, by binding nonspecifically to the membranes of excitable cells, reduce membrane fluidity and alter receptor function. The validity of this intriguing idea for NMDA receptor function is not well supported by two recent binding studies. Reynolds reported that argiotoxin 636 inhibits the binding of [3H]MK-801 to rat brain membranes in a manner that is insensitive to glutamate, glycine, or spermidine. This author concluded that argiotoxin 636 exerts a novel inhibitory effect on the NMDA receptor complex by binding to one of the Mg2+ sites located within the NMDA-gated ion channel. Binding data reported by Williams et al. also support the conclusion that argiotoxin 636 does not act primarily at the polyamine modulatory site on the NMDA receptor, but rather acts directly to produce an activity-dependent block of the ion channel. It is already known that compounds such as phencyclidine and ketamine can block the ion channels associated with both arthropod muscle glutamate receptors and mammalian NMDA receptors. Thus, it seems possible that vertebrate and invertebrate glutamate receptors share additional binding sites for allosteric modulators of receptor function, perhaps related to divalent cation-binding sites. Clearly, considerable additional work will be needed to determine if the arylamines define such a novel regulatory site.
Usherwood and Blagbrough (Spider Toxins Affecting Glutamate Receptors: Polyamines in Therapeutic Neurochemistry. Pharmacol. Therap. 52: 245, 1991) describe a proposed intracellular binding site for arylalkylamine toxins (polyamine amide toxins) located within the membrane potential field referred to as the QUIS-R channel selectivity filter. The authors postulate that the binding site for polyamine amide toxins may occur close to the internal entrance of the channel gated by the QUIS-R of locust muscle. The authors also note that one such toxin, argiotoxin-636, selectively antagonizes the NMDA receptor in cultured rat cortical neurons.
Gullak et al. (CNS binding sites of the novel NMDA antagonist Arg-636. Soc. Neurosci. Abst. 15: 1168, 1989), describe argiotoxin-636 (Arg-636) as a polyamine (arylalkylamine) toxin component of a spider venom. This toxin is said to block NMDA-induced elevation of cGMP in a noncompetitive fashion. The authors state that:
[125I]Arg-636 bound to rat forebrain membranes with Kd and Bmax values of 11.25 xcexcM and 28.95 pmol/mg protein (80% specific). The ability of other known polyamines and recently discovered polyamines from Agelenopsis aperta to inhibit binding paralleled neuroactivity as functional NMDA antagonists. No other compounds tested were able to block specific binding.
The authors then stated that polyamines (arylalkylamines) may antagonize responses to NMDA by interacting with membrane ion channels.
Seymour and Mena (In vivo NMDA antagonist activity of the polyamine spider venom component, argiotoxin-636. Soc. Neurosci. Abst. 15: 1168, 1989) describe studies that are said to show that argiotoxin-636 does not significantly affect locomotor activity at doses that are effective against audiogenic seizures in DBA/2 mice, and that it significantly antagonizes NMDA-induced seizures with a minimal effective dose of 32 mg/kg given subcutaneously (s.c.).
Herold and Yaksh (Anesthesia and muscle relaxation with intrathecal injections of AR636 and AG489, two acylpolyamine spider toxins, in rats. Anesthesiology 77: 507, 1992) describe studies that are said to show that the arylalkylamine argiotoxin-636 (AR636), but not agatoxin-489 (AG489), produces muscle relaxation and anesthesia following intrathecal administration in rats.
Williams (Effects of Agelenopsis aperta toxins on the N-methyl-D-aspartate receptor: Polyamine-like and high-affinity antagonist actions, J. Pharmacol. Exptl. Therap. 266: 231, 1993) reports that the xcex1-agatoxins (arylalkylamines) Agel-489 and Agel-505 enhance the binding of [3H]MK-801 to NMDA receptors on membranes prepared from rat brain by an action at the stimulatory polyamine receptor; polyamine receptor agonists occluded the stimulatory effects of Agel-489 and Agel-505 and polyamine receptor antagonists inhibited the stimulatory effect of Agel-505. Higher concentrations of Agel-489 and Agel-505, and argiotoxin-636 at all concentrations tested, had inhibitory effects on the binding of [3H]MK-801. In Xenopus oocytes voltage-clamped at xe2x88x9270 mV, Agel-505 inhibited responses to NMDA with an IC50 of 13 nM; this effect of Agel-505 occurred at concentrations approximately 10,000-fold lower than those that affected [3H]MK-801 binding. Responses to kainate were inhibited only 11% by 30 nM Agel-505. The antagonism of NMDA-induced currents by Agel-505 was strongly voltage-dependent, consistent with an open-channel blocking effect of the toxin. Williams states:
Although xcex1-agatoxins can interact at the positive allosteric polyamine site on the NMDA receptor, stimulatory effects produced by this interaction may be masked in functional assays due to a separate action of the toxins as high-affinity, noncompetitive antagonists of the receptor.
Brackley et al. (Selective antagonism of native and cloned kainate and NMDA receptors by polyamine-containing toxins, J. Pharmacol. Exp. Therap. 266: 1573, 1993) report that the polyamine-containing toxins (arylalkylamines) philanthotoxin-343 (PhTX-343) and argiotoxin-636 (Arg-636) produce reversible, noncompetitive, partly voltage-dependent antagonism of kainate- and NMDA-induced currents in Xenopus oocytes injected with rat brain RNA. Arg-636 was demonstrated to be selective for NMDA-induced responses (IC50=0.04 xcexcM) compared to kainate-induced responses (IC50=0.07 xcexcM), while PhTX-343 was selective for kainate-induced responses (IC50=0.12 xcexcM) compared to NMDA-induced responses (IC50=2.5 xcexcM). Arg-636 more potently antagonized responses to NMDA in Xenopus oocytes expressing cloned NMDAR1 subunits (IC50=0.09 xcexcM) than responses to kainate in oocytes expressing either cloned GluR1 (IC50=3.4 xcexcM) or GluR1+GluR2 subunits (IC50=300 xcexcM). PhTX-343, on the other hand, was equipotent at antagonizing NMDAR1 (IC50=2.19 xcexcM) and GluR1 (IC50=2.8 xcexcM), but much less potent against GluR1+GluR2 subunits (IC50=270 xcexcM).
Raditsch et al. (Subunit-specific block of cloned NMDA receptors by argiotoxin-636. FEBS Lett. 324: 63, 1993) report that Arg-636 more potently antagonizes responses in Xenopus oocytes expressing NMDAR1+NMDAR2A subunits (IC50=9 nM) or NMDAR1+NMDAR2B subunits (IC50=2.5 nM) than NMDAR1+NMDAR2C subunits (IC50=460 nM), even though all of the receptor subunits contain an asparagine residue in the putative pore-forming transmembrane region II (the Q/R site, as discussed above). The authors state that the large difference in Arg-636 sensitivity between NMDAR1+NMDAR2A and NMDAR1+NMDAR2C channels xe2x80x9cmust be conferred by other structural determinants.xe2x80x9d
Herlitz et al. (Argiotoxin detects molecular differences in AMPA receptor channels. Neuron 10: 1131, 1993) report that Arg-636 antagonizes subtypes of AMPA receptors in a voltage- and use-dependent manner consistent with open-channel blockade. Arg-636 potently antagonizes Ca2+-permeable AMPA receptors comprised of GluRAi (Ki=0.35 xcexcM), GluRCi (Ki=0.23 xcexcM), or GluRDi subunits (Ki=0.43 xcexcM), while being essentially ineffective against Ca2+-impermeable GluRBi subunits at concentrations up to 10 xcexcM.
Other data reported by these investigators strongly suggest that the Q/R site in the putative pore-forming transmembrane region II is of primary importance in determining Arg-636 potency and Ca2+ permeability.
Blaschke et al. (A single amino acid determines the subunit-specific spider toxin block of xcex1-amino-3-hydroxy-5-methylisoxazole-4-propionate/kainate receptor channels. Proc. Natl. Acad. Sci. USA 90: 6528, 1993) report that the arylalkylamine JSTX-3 potently antagonizes responses to kainate in Xenopus oocytes expressing GluR1 (IC50=0.04 xcexcM) or GluR3 (IC50=0.03 xcexcM) subunits, but that expressed receptors in which a GluR2 subunit is present are essentially unaffected by the toxin. Site-directed mutagenesis studies strongly implicate the Q/R site as the primary site influencing toxin potency.
Nakanishi et al. (Bioorganic studies of transmitter receptors with philanthotoxin analogs. Pure Appl. Chem., in press) have synthesized a number of highly potent photoaffinity labeled philanthotoxin (PhTX) analogs. Such analogs have been studied on expressed nicotinic cholinergic receptors as a model system for receptor-operated calcium channels. These investigators suggest that these PhTX analogs block the ion channel with the hydrophobic headpiece of the toxin binding to a site near the cytoplasmic surface while the polyamine tail extends into the ion channel from the cytoplasmic side.
Applicant has examined the structural diversity and biological activity of arylalkylamines (sometimes referred to as arylamine toxins, polyamine toxins, acylpolyamine toxins or polyamine amide toxins) in spider and wasp venoms, and determined that some of the arylalkylamines present in these venoms act as potent noncompetitive antagonists of glutamate receptor-operated Ca2+ channels in the mammalian CNS. Although these arylalkylamine compounds contain within their structure a polyamine moiety, they are unlike other known simple polyamines in possessing extremely potent and specific effects on certain types of receptor-operated Ca2+ channels.
Using native arylalkylamines as lead structures, a number of analogs were synthesized and tested. Initial findings on arylalkylamines isolated and purified from venom were confirmed utilizing synthetic arylalkylamines. These compounds are small molecules (mol. wt.  less than 800) with demonstrated efficacy in in vivo models of stroke and epilepsy. The NMDA receptor-ionophore complex was used as a model of receptor-operated Ca2+ channels. Selected arylalkylamines were shown to block NMDA receptor-mediated responses by a novel mechanism. Moreover, the unique behavioral pharmacological profile of these compounds suggests that they are unlikely to cause the PCP-like psychotomimetic activity and cognitive deficits that characterize other inhibitors of the NMDA receptor. Finally, the arylalkylamines are unique amongst NMDA receptor antagonists in that they are able to antagonize certain subtypes of cloned and expressed AMPA receptors, namely, those permeable to Ca2+. The arylalkylamines, therefore, are the only known class of compounds able to antagonize glutamate receptor-mediated increases in cytosolic Ca2+ regardless of the pharmacological definition of receptor subtype. Additionally, the arylalkylamines inhibit another receptor-operated Ca2+ channel, the nicotinic cholinergic receptor. Given that excessive and prolonged increases in cytosolic Ca2+ have been implicated in the etiology of several neurological disorders and diseases, such arylalkylamines are valuable small molecule leads for the development of novel therapeutics for various neurological disorders and diseases.
Applicant has determined that the selected arylalkylamines bind with high affinity at a novel site on the NMDA receptor-ionophore complex which has heretofore been unidentified, and that said arylalkylamines do not bind with high affinity at any of the known sites (glutamate binding site, glycine binding site, MK-801 binding site, Mg2+ binding site, Zn2+ binding site, polyamine binding site, sigma binding site) on said NMDA receptor-ionophore complex. This determination has allowed applicant to develop methods and protocols by which useful compounds can be identified which provide both therapeutically useful compounds and lead compounds for the development of other therapeutically useful compounds. These compounds can be identified by screening for compounds that bind at this novel arylalkylamine binding site, and by determining whether such a compound has the required biological, pharmacological and physiological properties.
The method includes the step of identifying a compound which binds to the receptor-operated Ca2+ channel at that site bound by the arylalkylamine compounds referred to herein as Compound 1, Compound 2 or Compound 3, and having the structures shown below. 
By xe2x80x9ctherapeutically useful compoundxe2x80x9d is mean; a compound that is potentially useful in the treatment of a disorder or disease state. A compound uncovered by the screening method is characterized as having potential therapeutic utility in treatment because clinical tests have not yet been conducted to determine actual therapeutic utility.
By xe2x80x9cneurological disorder or diseasexe2x80x9d is meant a disorder or disease of the nervous system including, but not limited to, global and focal ischemic and hemorrhagic stroke, head trauma, spinal cord injury, spinal cord ischemia-, ischemia- or hypoxia-induced nerve cell damage, hypoxia-induced nerve cell damage as in cardiac arrest or neonatal distress, epilepsy, anxiety, neuropsychiatric or cognitive deficits due to ischemia or hypoxia such as those that frequently occur as a consequence of cardiac surgery under cardiopulmonary bypass, and neurodegenerative disease. Also meant by xe2x80x9cneurological disorder or diseasexe2x80x9d are those disease states and conditions in which a neuroprotectant, anticonvulsant, anxiolytic, analgesic, muscle relaxant and/or adjunct in general anesthesia may be indicated, useful, recommended or prescribed.
By xe2x80x9cneurodegenerative diseasexe2x80x9d is meant diseases including, but not limited to, Alzheimer""s Disease, Huntington""s Disease, Parkinson""s Disease, and amyotrophic lateral sclerosis (ALS).
By xe2x80x9cneuroprotectantxe2x80x9d is meant a compound capable of preventing the neuronal damage or death associated with a neurological disorder or disease.
By xe2x80x9canticonvulsantxe2x80x9d is meant a compound capable of reducing convulsions produced by conditions such as simple partial seizures, complex partial seizures, status epilepticus, and trauma-induced seizures such as occur following head injury, including head surgery.
By xe2x80x9canxiolyticxe2x80x9d is meant a compound capable of relieving the feelings of apprehension, uncertainty and fear that are characteristic of anxiety.
By xe2x80x9canalgesicxe2x80x9d is meant a compound capable of relieving pain by altering perception of nociceptive stimuli without producing anesthesia or loss of consciousness.
By xe2x80x9cmuscle relaxantxe2x80x9d is meant a compound that reduces muscular tension.
By xe2x80x9cadjunct in general anesthesiaxe2x80x9d is meant a compound useful in conjunction with anesthetic agents in producing the loss of ability to perceive pain associated with the loss of consciousness.
By xe2x80x9cpotentxe2x80x9d or xe2x80x9cactivexe2x80x9d is meant that the compound has activity at receptor-operated calcium channels, including NMDA receptors, Ca2+-permeable AMPA receptors, and nicotinic cholinergic receptors, with an IC50 value less than 10 xcexcM, more preferably less than 100 nM, and even more preferably less than 1 nM.
By xe2x80x9cselectivexe2x80x9d is meant that the compound is potent at receptor-operated calcium channels as defined above, but is less potent by greater than 10-fold, more preferably 50-fold, and even more preferably 100-fold, at other neurotransmitter receptors, neurotransmitter receptor-operated ion channels, or voltage-dependent ion channels.
By xe2x80x9cbiochemical and electrophysiological assays of receptor-operated calcium channel functionxe2x80x9d is meant assays designed to detect by biochemical or electrophysiological means the functional activity of receptor-operated calcium channels. Examples of such assays include, but are not limited to, the fura-2 fluorimetric assay for cytosolic calcium in cultured rat cerebellar granule cells (see Example 1 and Example 2), patch clamp electrophysiolocial assays (see Example 3 and Example 27), rat hippocampal slice synaptic transmission assays (see Example 5), radioligand binding assays (see Example 4, Example 24, Example 25, and Example 26), and in vitro neuroprotectant assays (see Example 6).
By xe2x80x9cefficacyxe2x80x9d is meant that a statistically significant level of the desired activity is detectable with a chosen compound; by xe2x80x9csignificantxe2x80x9d is meant a statistical significance at the p less than 0.05 level.
By xe2x80x9cneuroprotectant activityxe2x80x9d is meant efficacy in treatment of neurological disorders or diseases including, but not limited to, global and focal ischemic and hemorrhagic stroke, head trauma, spinal cord injury, spinal cord ischemia, ischemia- or hypoxia-induced nerve cell damage, hypoxia-induced nerve cell damage as in cardiac arrest or neonatal distress, neuropsychiatric or cognitive deficits due to ischemia or hypoxia such as those that frequently occur as a consequence of cardiac surgery under cardiopulmonary bypass, and neurodegenerative diseases such as Alzheimer""s Disease, Huntington""s Disease, Parkinson""s Disease, and amyotrophic lateral sclerosis (ALS) (see Examples 7 and 8, below).
By xe2x80x9canticonvulsant activityxe2x80x9d is meant efficacy in reducing convulsions produced by conditions such as simple partial seizures, complex partial seizures, status epilepticus, and trauma-induced seizures such as occur following head injury, including head surgery (see Examples 9 and 10, below).
By xe2x80x9canxiolytic activityxe2x80x9d is meant that a compound reduces the feelings of apprehension, uncertainty and fear that are characteristic of anxiety.
By xe2x80x9canalgesic activityxe2x80x9d is meant that a compound produces the absence of pain in response to a stimulus that would normally be painful. Such activity would be useful in clinical conditions of acute and chronic pain including, but not limited to the following: preemptive preoperative analgesia; peripheral neuropathies such as occur with diabetes mellitus and multiple sclerosis; phantom limb pain; causalgia; neuralgias such as occur with herpes zoster; central pain such as that seen with spinal cord lesions; hyperalgesia; and allodynia.
By xe2x80x9ccausalgiaxe2x80x9d is meant a painful disorder associated with injury of peripheral nerves.
By xe2x80x9cneuralgiaxe2x80x9d is meant pain in the distribution of a nerve or nerves.
By xe2x80x9ccentral painxe2x80x9d is meant pain associated with a lesion of the central nervous system.
By xe2x80x9chyperalgesiaxe2x80x9d is meant an increased response to a stimulus that is normally painful.
By xe2x80x9callodyniaxe2x80x9d is meant pain due to a stimulus that does not normally provoke pain (see Examples 11 through 14, below).
By xe2x80x9cinduction of long-term potentiation in rat hippocampal slicesxe2x80x9d is meant the ability of tetanic electrical stimulation of afferent Schaffer collateral fibers to elicit long-term increases in the strength of synaptic transmission at the Schaffer collateral-CA1 pyramidal cell pathway in rat hippocampal slices maintained in vitro (see Example 19).
By xe2x80x9ctherapeutic dosexe2x80x9d is meant an amount of a compound that relieves to some extent one or more symptoms of the disease or condition of the patient. Additionally, by xe2x80x9ctherapeutic dosexe2x80x9d is meant an amount that returns to normal, either partially or completely, physiological or biochemical parameters associated with or causative of the disease or condition. Generally, it is an amount between about 1 nmole and 1 xcexcmole of the compound, dependent on its EC50 (IC50 in the case of an antagonist) and on the age, size, and disease associated with the patient.
By xe2x80x9cimpair cognitionxe2x80x9d is meant the ability to impair the acquisition of memory or the performance of a learned task (see Example 20). Also by xe2x80x9cimpair congnitionxe2x80x9d is meant the ability to interfere with normal rational thought processes and reasoning.
By xe2x80x9cdisrupt motor functionxe2x80x9d is meant the ability to significantly alter locomotor activity (see Example 15) or elicit significant ataxia, loss of the righting reflex, sedation or muscle relaxation (see Example 16).
By xe2x80x9clocomotor activityxe2x80x9d is meant the ability to perform normal ambulatory movements.
By xe2x80x9closs of the righting reflexxe2x80x9d is meant the ability of an animal, typically a rodent, to right itself after being placed in a supine position.
By xe2x80x9cneuronal vacuolizationxe2x80x9d is meant the production of vacuoles in neurons of the cingulate cortex or retrosplenial cortex (see Example 18).
By xe2x80x9ccardiovascular activityxe2x80x9d is meant the ability to elicit significant changes in parameters including, but not limited to, mean arterial blood pressure and heart rate (see Examples 21 and 22).
By xe2x80x9chyperexcitabilityxe2x80x9d is meant an enhanced susceptibility to an excitatory stimulus. Hyperexcitability is often manifested as a significant increase in locomotor activity in rodents administered a drug (see Example 15).
By xe2x80x9csedationxe2x80x9d is meant a calmative effect, or the allaying of activity and excitement. Sedation is often manifested as a significant decrease in locomotor activity in rodents administered a drug (see Example 15).
By xe2x80x9cPCP-like abuse potentialxe2x80x9d is meant the potential of a drug to be wrongfully used, as in the recreational use of PCP (i.e., xe2x80x9cangel dustxe2x80x9d) by man. It is believed that PCP-like abuse potential can be predicted by the ability of a drug to generalize to PCP in rodents trained to discriminate PCP from saline (see Example 17.)
By xe2x80x9cgeneralization to PCPxe2x80x9d is meant that a compound is perceived as being PCP in rodents trained to discriminate PCP from saline (see Example 17).
By xe2x80x9cPCP-like psychotomimetic activityxe2x80x9d is meant the ability of a drug to elicit in man a behavioral syndrome resembling acute psychosis, including visual hallucinations, paranoia, agitation, and confusion. It is believed that PCP-like psychotomimetic activity can be predicted in rodents by the ability of a drug to produce PCP-like stereotypic behaviors including ataxia, head weaving, hyperexcitability, and generalization to PCS in rodents trained to discriminate PCP from saline (see Example 15, Example 16, and Example 17).
By xe2x80x9cataxiaxe2x80x9d is meant a deficit in muscular coordination.
By xe2x80x9chead weavingxe2x80x9d is meant the stereotypic behavior elicited in rodents by PCP in which the head is repeatedly moved slowly and broadly from side to side.
By xe2x80x9cpharmaceutical compositionxe2x80x9d is meant a therapeutically effective amount of a compound of the present invention in a pharmaceutically acceptable carrier; i.e., a formulation to which the compound can be added to dissolve or otherwise facilitate administration of the compound. Examples of pharmaceutically acceptable carriers include water, saline, and physiologically buffered saline. Such a pharmaceutical composition is provided in a suitable dose. Such compositions are generally those which are approved for use in treatment of a specified disorder by the FDA or its equivalent in non-U.S. countries.
In a related aspect, the invention features a method for treating a neurological disease or disorder, comprising the step of administering a pharmaceutical composition comprising a compound which binds to a receptor-operated calcium channel at the site bound by one of the arylalkylamines Compound 1, Compound 2 and Compound 3, said compound being a potent and selective noncompetitive antagonist at such a receptor-operated calcium channel, and having one or more of the following pharmacological and physiological properties: efficacy in in vitro biochemical and electrophysiological assays of receptor-operated calcium channel function, in vivo anticonvulsant activity, in vivo neuroprotectant activity, in vivo anxiolytic activity, and in vivo analgesic activity; said compound also possessing one or more of the following pharmacological effects: the compound does not interfere with the induction of long-term potentiation in rat hippocampal slices, and, at a therapeutic dose, does not impair cognition, does not disrupt motor performance, does not produce neuronal vacuolization, has minimal cardiovascular activity, does not produce sedation or hyperexcitability, has minimal PCP-like abuse potential, and has minimal PCP-like psychotomimetic activity. By xe2x80x9cminimalxe2x80x9d is meant that any side effect of the drug is tolerated by an average individual, and thus that the drug can be used for therapy of the target disease. Such side effects are well known in the art and are routinely regarded by the FDA as minimal when it approves a drug for a target disease.
Treatment involves the steps of first identifying a patient that suffers from a neurological disease or disorder by standard clinical methodology and then treating such a patient with a composition of he present invention.
In a further aspect, the invention features compounds useful for treating a patient having a neurological disease or disorder wherein said compound is a polyamine-type compound or an analog thereof (i.e., a polyheteroatomic molecule) having the formula 
wherein Ar is an appropriately substituted aromatic ring, ring system or other hydrophobic entity; Ar can be an aromatic (e.g., carbocyclic aryl groups such as phenyl and bicyclic carbocyclic aryl ring systems such as naphthyl, 1,2,3,4-tetrahydronaphthyl, indanyl, and indenyl), heteroaromatic (e.g., indolyl, dihydroindolyl, quinolinyl and isoquinolinyl, and their respective 1,2,3,4-tetrahydro- and 2-oxo-derivatives), alicyclic (cycloaliphatic), or heteroalicyclic ring or ring system (mono-, bi-, or tricyclic), having 5- to 7-membered ring(s) optionally substituted with 1 to 5 substituents independently selected from lower alkyl of 1 to 5 carbon atoms, lower haloalkyl of 1 to 5 carbon atoms substituted with 1 to 7 halogen atoms, lower alkoxy of 1 to 5 carbon atoms, halogen, nitro, amino, lower alkylamino of 1 to 5 carbon atoms, amido, lower alkylamido of 1 to 5 carbon atoms, cyano, hydroxyl, sulfhydryl, lower acyl of 2 to 4 carbon atoms, sulfonamido, lower alkylsulfonamido of 1 to 5 carbon atoms, lower alkylsulfoxide of 1 to 5 carbon atoms, lower hydroxyalkyl of 1 to 5 carbon atoms, lower alkylketo of 1 to 5 carbon atoms, or lower thioalkyl of 1 to 5 carbon atoms,
each m is an integer from 0 to 3, inclusive,
each k is an integer from 1 to 10, inclusive,
each j is the same or different and is an integer from 1 to 12, inclusive,
each R1 and R2 independently is selected from the group consisting of hydrogen, lower alkyl of 1 to 5 carbon atoms, lower alkylamino of 1 to 5 carbon atoms, lower alkylamido of 1 to 5 carbon atoms, lower mono-, di-, or trifluoroalkyl of 1 to 5 carbon atoms, hydroxy, amidino, guanidino, or typical common amino acid side chain or with an associated carbon atom R1 and R2 taken together form a carbonyl, and
each Z is selected from the group consisting of nitrogen, oxygen, sulfur, amido, sulfonamido, and carbon.
Preferred aromatic headgroups include, but are not limited to, the following: 
Preferably the claims claiming a compound exclude known compounds whose chemical structures are enabled.
In further preferred embodiments, the compound is selected from the group of Compounds 4 through 18, where such compounds have the formulae: 
Applicant has also determined (see Example 23 below) that simplified arylalkylamines (see below) are potent, noncompetitive antagonists of the NMDA receptor-ionophore complex. The simplified arylalkylamines are distinct from the arylalkylamines exemplified by Compounds 4-18 as described above. For example; such compounds bind to the site labeled by [3H]MK-801 at concentrations ranging approximately 1 to 400-fold higher than those which antagonize NMDA receptor-mediated function. Such simplified arylalkylamines possess one or more of the following additional biological properties: significant neuroprotectant activity, significant anticonvulsant activity, significant analgesic activity, no PCP-like stereotypic behavior in rodents (hyperexcitability and head weaving) at effective neuroprotectant, anticonvulsant and analgesic doses, no generalization to PCP in a PCP discrimination assay at effective neuroprotectant, anticonvulsant and analgesic doses, no neuronal vacuolization at effective neuroprotectant, anticonvulsant and analgesic doses, significantly less potent activity against voltage-sensitive calcium channels, and minimal hypotensive activity at effective neuroprotectant, anticonvulsant and analgesic doses. Such compounds may, however, inhibit the induction of LTP in rat hippocampal slices and may produce motor impairment at neuroprotectant, anticonvulsant and analgesic doses.
One aspect of the invention features a method for treating a patient having a neurological disease or disorder, comprising administering a compound of Formula I: 
wherein:
R1 and R5 are independently selected from the group consisting of phenyl, benzyl, and phenoxy (each of which is optionally substituted with alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, xe2x80x94O-acyl, xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, or xe2x80x94OCF3), xe2x80x94H, alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and O-acyl;
R2 and R6 are independently selected from the group consisting of xe2x80x94H, alkyl, and hydroxyalkyl; or R2 and R6 together are imino; or R1 and R2 together are xe2x80x94(CH2)nxe2x80x94 or xe2x80x94(CH2)nxe2x80x94N(R3)xe2x80x94(CH2)nxe2x80x94;
R3 is independently selected from the group consisting of xe2x80x94H, alkyl, 2-hydroxyethyl and alkylphenyl;
n is an integer from 0 to 6, but at least one n must be greater than 0;
R4 is selected from the group consisting of thiofuran, pyridyl, phenyl, benzyl, phenoxy, and phenylthio (each of which is optionally substituted with alkyl, xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, or xe2x80x94O-acyl), xe2x80x94H, alkyl and cycloalkyl;
X is independently selected from the group consisting of phenyl, benzyl, and phenoxy (each of which is optionally substituted with xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, or xe2x80x94O-acyl) xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, and O-acyl;
m is independently an integer from 0 to 5;
Y is xe2x80x94NR3R3, except when R1 and R2 together are xe2x80x94(CH2)nxe2x80x94N(R3)xe2x80x94(CH2)nxe2x80x94, then Y is xe2x80x94H;
and pharmaceutically acceptable salts and complexes thereof, wherein the compound is active at an NMDA receptor.
By xe2x80x9cpatientxe2x80x9d is meant any animal that has a cell with an NMDA receptor. Preferably, the animal is a mammal. Most preferably, the animal is a human.
By xe2x80x9calkylxe2x80x9d is meant a branched or unbranched hydrocarbon chain containing between 1 and 6, preferably between 1 and 4, carbon atoms, such as, e.g., methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, 2-methylpentyl, cyclopropylmethyl, allyl, and cyclobutylmethyl.
By xe2x80x9clower alkylxe2x80x9d is meant a branched or unbranched hydrocarbon chain containing between 1 and 4 carbon atoms, of which examples are listed herein.
By xe2x80x9chydroxyalkylxe2x80x9d is meant an alkyl group as defined above, substituted with a hydroxyl group.
By xe2x80x9calkylphenylxe2x80x9d is meant an alkyl group as defined above, substituted with a phenyl group.
By xe2x80x9cacylxe2x80x9d is meant xe2x80x94C(O)R, where R is H or alkyl as defined above, such as, e.g., formyl, acetyl, propionyl, or butyryl; or,
R is xe2x80x94O-alkyl such as in alkyl carbonates or R is N-alkyl such as in alkyl carbamates.
By xe2x80x9ccycloalkylxe2x80x9d is meant a branched or unbranched cyclic hydrocarbon chain containing between 3 and 12 carbon atoms.
In preferred aspects of the invention,
Y is selected from the group consisting of xe2x80x94NH2 and xe2x80x94NH-methyl;
R4 is thiofuran, pyridyl, phenyl, benzyl, phenoxy, or phenylthio, each of which is optionally substituted with xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, or xe2x80x94O-acyl;
X is independently selected from the group consisting of meta-fluoro, meta-chloro, ortho-O-lower alkyl, ortho-methyl, ortho-fluoro, ortho-chloro, meta-O-lower alkyl, meta-methyl, ortho-OH, and meta-OH; and either
R1, R2, R5, and R6 are xe2x80x94H;
or R2 is methyl, and R1, R5, and R6 are xe2x80x94H;
or R1 is methyl, and R2, R5, and R6 are xe2x80x94H.
In other preferred aspects of the present invention,
R1 and R5 are independently selected from the group consisting of xe2x80x94H, lower alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R2 and R6 are independently selected from the group consisting of xe2x80x94H, lower alkyl, and hydroxyalkyl;
or R1 and R2 together are xe2x80x94(CH2)nxe2x80x94 or xe2x80x94(CH2)nxe2x80x94N(R3)xe2x80x94, and Y is H;
R3 is independently selected from the group consisting of xe2x80x94H and lower alkyl;
R4 is selected from the group consisting of thiofuran, pyridyl, phenyl, benzyl, phenoxy, and phenylthio (each of which is optionally substituted with lower alkyl, xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, or xe2x80x94O-acyl), xe2x80x94H, lower alkyl, and cycloalkyl;
X is independently selected from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, lower alkyl, xe2x80x94OH, and xe2x80x94OCF3;
m is independently an integer from 0 to 5;
Y is xe2x80x94NHR3, or hydrogen when R1 and R2 together are xe2x80x94(CH2)nxe2x80x94N(R3)xe2x80x94, and pharmaceutically acceptable salts and complexes thereof, with the provisos that
(a) when R1 and R2 together are xe2x80x94(CH2)nxe2x80x94N(R3)xe2x80x94, then R5, R6, and Y are hydrogens; and
(b) when R1 and R2 together are not (CH2)nxe2x80x94N(R3)xe2x80x94, then Y is xe2x80x94NHR3.
In one preferred aspect, the invention features a method for treating a patient having a neurological disease or disorder comprising administering a compound of Formula II: 
wherein:
X is independently selected from the group consisting of xe2x80x94H, xe2x80x94Br, xe2x80x94Cl, xe2x80x94F, xe2x80x94I, xe2x80x94CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R1 is independently selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R2 is independently selected from the group consisting of xe2x80x94H, alkyl, and hydroxyalkyl, or both R2s together are imino; R3 is independently selected from the group consisting of xe2x80x94H, alkyl, 2-hydroxyethyl, and alkylphenyl; and m is independently an integer from 0 to 5.
Thus, in this preferred aspect, the compounds include the compound of Formula I, wherein:
X is independently selected from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R1 is selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R2 and R6 are independently selected from the group consisting of xe2x80x94H, alkyl, and hydroxyalkyl, or R2 and R6 together are imino;
R5 is selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
Y is NR3R3; and
R4 is phenyl, optionally substituted with alkyl, xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, or xe2x80x94O-acyl.
In another preferred aspect, the administered compound has the structure of Formula III: 
wherein:
X is independently selected from the group consisting of xe2x80x94H, xe2x80x94Br, xe2x80x94Cl, xe2x80x94F, xe2x80x94I, xe2x80x94CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R1 is independently selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R2 is independently selected from the group consisting of xe2x80x94H, alkyl, and hydroxyalkyl, or both R2s together, are imino;
R3 is independently selected from the group consisting of xe2x80x94H, alkyl, 2-hydroxyethyl, and alkylphenyl;
R4 is selected from the group consisting of thiofuran, pyridyl, phenyl, benzyl, phenoxy, and phenylthio, (each of which is optionally substituted with (X)m), alkyl, and cycloalkyl; and, m is independently an integer from 0 to 5.
Thus, in the preferred aspect, the compounds include the compound of Formula I, wherein:
X is independently selected from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R1 is selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R2 and R6 are selected from the group consisting of xe2x80x94H, alkyl, and hydroxyalkyl, or R2 and R6 together are imino;
R5 is independently selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and xe2x80x94O-acyl; and
Y is NR3R3.
In another preferred aspect, the administered compound has the structure of Formulas IV and V. 
wherein:
n is an integer from 1 to 6;
X is independently selected from the group consisting of xe2x80x94H, xe2x80x94Br, xe2x80x94Cl, xe2x80x94F, xe2x80x94I xe2x80x94CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R3 is independently selected from the group consisting of xe2x80x94H, alkyl, 2-hydroxyethyl, and alkylphenyl; and m is independently an integer from 0 to 5.
Thus, in this preferred aspect, the administered compounds include the compound of Formula I, wherein:
R3 is independently selected from the group consisting of xe2x80x94H, and alkyl;
R4 is phenyl, optionally substituted with alkyl, xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, or xe2x80x94O-acyl: and
R1 and R2 together are xe2x80x94(CH2)nxe2x80x94 or xe2x80x94(CH2)nxe2x80x94N(R3)xe2x80x94.
In another preferred aspect, the administered compound has the structure of Formulas VI and VII: 
wherein:
n is an integer from 1 to 6;
X is independently selected from the group consisting of xe2x80x94H, xe2x80x94Br, xe2x80x94Cl, xe2x80x94F, xe2x80x94I, xe2x80x94CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, and xe2x80x94O-acyl;
R3 is independently selected from the group consisting of xe2x80x94H, alkyl, 2-hydroxyethyl, and alkylphenyl;
R4 is selected from the group consisting of thiofuran, pyridyl, phenyl, benzyl, phenoxy, and phenylthio (each of which is optionally substituted with (X)m), alkyl, and cycloalkyl; and m is independently an integer from 0 to 5.
Thus, in this preferred aspect, the administered compounds include the compound of Formula I, wherein:
X is independently selected from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, CF3, alkyl, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, and xe2x80x94O-acyl-; and
R1 and R2 together are xe2x80x94(CH2)nxe2x80x94 or xe2x80x94(CH2)nxe2x80x94N(R3)xe2x80x94.
More preferred aspects are those embodiments in which:
X is independently selected from the group consisting of meta-fluoro, meta-chloro, ortho-O-lower alkyl, ortho-methyl, ortho-fluoro, ortho-chloro, meta-O-lower alkyl, meta-methyl, ortho-OH, and meta-OH;
NR3 is selected from the group consisting of NH, N-methyl, and N-ethyl;
NR3R3 is selected from the group consisting of NH2, NH-methyl, and NH-ethyl;
R1 is selected from the group consisting of xe2x80x94H and methyl;
R2 is selected from the group consisting of xe2x80x94H and methyl; and
R4 is selected from the group consisting of phenyl, benzyl, and phenoxy, each of which is optionally substituted with alkyl, xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94F, xe2x80x94CF3, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, or xe2x80x94O-acyl.
Especially preferred aspects are those embodiments in which:
X is meta-fluoro;
each R1 and R2 is xe2x80x94H;
NR3 is selected from the group consisting of NH and N-methyl;
NR3R3 is selected from the group consisting of NH2 and NH-methyl; and
R4 is selected from the group consisting of phenyl, benzyl, and phenoxy, each of which is optionally substituted with alkyl, xe2x80x94F, xe2x80x94Cl, xe2x80x94Br, xe2x80x94I, xe2x80x94CF3, xe2x80x94OH, xe2x80x94OCF3, xe2x80x94O-alkyl, or xe2x80x94O-acyl.
In a further aspect, the invention features a method for treating a patient having a neurological disease or disorder comprising administering the compounds of Formula VIII: 
wherein:
Z is selected from the group consisting of xe2x80x94CH2CH2xe2x80x94, xe2x80x94CH2CH(CH3)xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Oxe2x80x94CH2xe2x80x94, xe2x80x94Sxe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, and xe2x80x94Sxe2x80x94;
X1 and X2 are independently selected from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94CH3, xe2x80x94OH, and lower O-alkyl in the 1-, 3-, 7-, or 9-substituent positions;
m is independently an integer from 0 to 2;
xe2x80x94NHR is selected from the group consisting of xe2x80x94NH2, xe2x80x94NHCH3, and xe2x80x94NHC2H5;
R1 is selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and xe2x80x94O-acyl, and
R2 is selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, and pharmaceutically acceptable salts and complexes thereof, wherein the compound is active at an NMDA receptor.
Especially preferred aspects are those embodiments in which:
Z is xe2x80x94CH2CH2xe2x80x94;
X1 or X2 is xe2x80x94F, or both X1 and X2 are xe2x80x94F;
either R1 or R2 is methyl or both R1 and R2 are xe2x80x94H; and
xe2x80x94NHR is selected from the group consisting of xe2x80x94NH2 or xe2x80x94NHCH3.
In other preferred embodiments, the invention features a method for treating a patient having a neurological disease or disorder comprising administering the compounds of Formula IX: 
wherein:
W is selected from the group consisting of xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, and xe2x80x94Sxe2x80x94;
X1 and X2 are independently selected from the group consisting of xe2x80x94F, xe2x80x94Cl, xe2x80x94CH3, xe2x80x94OH, and lower O-alkyl;
m is independently an integer from 0 to 2;
xe2x80x94NHR is selected from the group consisting of xe2x80x94NH2, xe2x80x94NHCH3, and xe2x80x94NHC2H5;
R1 is selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, xe2x80x94OH, xe2x80x94O-alkyl, and xe2x80x94O-acyl; and
R2 is selected from the group consisting of xe2x80x94H, alkyl, hydroxyalkyl, and pharmaceutically acceptable salts and complexes thereof, wherein the compound is active at an NMDA receptor.
In preferred aspects, the administered compound is selected from the group consisting of Compound 128, 129, 130, 131, 132, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, and 215.
In preferred embodiments, the methods of treatment include administration of a compound selected from Compounds 29 through 215, or pharmaceutically acceptable salts and complexes thereof. Preferably, the compound has an IC50xe2x89xa610 xcexcM at an NMDA receptor, more preferably xe2x89xa62.5 xcexcM, and most preferably xe2x89xa60.5 xcexcM at an NMDA receptor.
In further preferred embodiments, the methods of treatment include administration of a compound selected from the group consisting of Compound 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 75, 76, 77, 78, 79, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 100, 101, 102, 103, 105, 106, 107, 108, 109, 111, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138 (potential prodrug), 139, 141, 142, 143, 144, 145, 146, 147, 148, 149, and 150, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa610 xcexcm at an NMDA receptor.
In more preferred embodiments, the methods of treatment include administration of a compound selected from the group consisting of Compound 19, 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 70, 75, 76, 81, 82, 83, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 100, 101, 102, 103, 105, 106, 108, 109, 111, 115, 118, 119, 120, 121, 122, 125, 126, 127, 128, 129, 130, 131, 132, 133, 135, 136, 137, 138 (potential prodrug), 139, 142, 144, 145, 146, 147, 148, 149, and 150, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa62.5 xcexcM at an NMDA receptor
In other embodiments, the compound is selected from the group consisting of Compound 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 76, 82, 83, 88, 89, 90, 92, 93, 94, 95, 96, 101, 102, 103, 105, 109, 111, 115, 118, 119, 120, 121, 122, 125, 126, 127, 129, 130, 131, 135, 136, 137, 138, 139, 142, 144, 145, 148, 149, and 150, and pharmaceutically acceptable salts and complexes thereof.
In particularly preferred embodiments, the methods of treatment include administration of a compound selected from the group consisting of Compound 19, 20, 21, 22, 23, 24, 25, 27, 28, 30, 31, 32, 33, 38, 39, 43, 44, 46, 47, 49, 50, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 82, 83, 89, 90, 91, 93, 94, 95, 96, 97, 103, 111, 118, 119, 120, 122, 126, 135, 136, 137, 138 (potential prodrug), 142, 144, 145, 147, 148, 149, and 150, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa60.5 xcexcM at an NMDA receptor.
In more preferred embodiments, the methods of treatment include administration of a compound selected from the group consisting of Compound 20, 24, 25, 33, 50, 60, 66, 69, 103, 111, 118, 119, 120, 122, 136, 137, 138 (potential prodrug), 142, 144, 145, 148, 149, and 150, and pharmaceutically acceptable salts and complexes thereof.
In particularly preferred embodiments, the methods of treatment include administration of a compound selected from the group consisting of compound 20, 33, 50, 60, 119, and 144, and pharmaceutically acceptable salts and complexes thereof.
In other particularly preferred embodiments, the methods of treatment include administration of a compound selected from the group consisting of compound 33, 50, 60, 119, and 144, and pharmaceutically acceptable salts and complexes thereof.
In preferred aspects, the invention provides a method for treating a patient having a neurological disease or disorder, comprising administering a compound which is selected from the group consisting of Compound 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 181, 182, 183, 184, 185, 186, 187, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa610 xcexcM at an NMDA receptor.
In further preferred aspects, the invention provides a method for treating a patient having a neurological disease or disorder, comprising administering a compound which is selected from the group consisting of Compound 157, 158, 159, 163, 164, 166, 167, 168, 169, 170, 171, 181, 185, 186, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa610 xcexcM at an NMDA receptor.
In other more preferred aspects, the invention provides a method for treating a patient having a neurological disease or disorder, comprising administering a compound which is selected from the group consisting of Compound 156, 157, 158, 159, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 181, 183, 184, 185, 186, 187, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa62.5 xcexcM at an NMDA receptor.
In further preferred aspects, the invention provides a method for treating a patient having a neurological disease or disorder, comprising administering a compound which is selected from the group consisting of Compound 157, 158, 159, 163, 164, 166, 167, 168, 169, 170, 171, 181, 185, 186, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa62.5 xcexcM at an NMDA receptor.
In other particularly preferred aspects, the invention provides a method for treating a patient having a neurological disease or disorder, comprising administering a compound which is selected from the group consisting of Compound 156, 157, 158, 159, 161, 163, 164, 165, 167, 168, 169, 170, 171, 181, 186 and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa60.5 xcexcM at an NMDA receptor.
In further preferred aspects, the invention provides a method for treating a patient having a neurological disease or disorder, comprising administering a compound which is selected from the group consisting of Compound 157, 158, 159, 163, 164, 167, 168, 169, 170, 171, 181, 186 and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa60.5 xcexcM at an NMDA receptor.
In other preferred aspects, the invention provides a method for treating a patient having a neurological disease or disorder comprising administering a compound selected from the group consisting of Compounds 151-215, and pharmaceutically acceptable salts and complexes thereof.
In more preferred aspects, the invention provides a method for treating a patient having a neurological disease or disorder comprising administering a compound selected from the group consisting of Compound 151, 152, 153, 154, 155, 157, 158, 159, 163, 164, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 181, 185, 186, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215 and pharmaceutically acceptable salts and complexes thereof.
The present invention provides simplified arylalkylamines comprising the compounds of Formulas I-IX and all preferred aspects of Formulas I-IX as set out above.
Examples of such simplified arylalkylamines include, but are not limited to, Compounds 19-215, whose structures are provided below. Preferably, the compound has an IC50xe2x89xa610 xcexcM at an NMDA receptor. More preferably, the compound has an IC50xe2x89xa65 xcexcM, more preferably xe2x89xa62.5 xcexcM, and most preferably xe2x89xa60.5 xcexcM at an NMDA receptor.
In preferred embodiments, the compound is selected from the group consisting of Compound 21, 22, 23, 24, 25, 26, 27, 28, 29, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 76, 78, 79, 82, 83, 84, 88, 89, 90, 92, 93, 94, 95, 96, 98, 101, 102, 103, 105, 107, 108, 109, 111, 115, 116, 118, 119, 120, 121, 122, 124, 125, 126, 127, 129, 130, 131, 134, 135, 136, 137, 138 (potential prodrug), 139, 141, 142, 143, 144, 145, 148, 149, and 150. These compounds have an IC50xe2x89xa610 xcexcM at an NMDA receptor.
In other embodiments, the compound is selected from the group consisting of Compound 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 76, 82, 83, 88, 89, 90, 92, 93, 94, 95, 96, 101, 102, 103, 105, 109, 111, 115, 118, 119, 120, 121, 122, 125, 126, 127, 129, 130, 131, 135, 136, 137, 138, 139, 142, 144, 145, 148, 149, and 150.
In more preferred embodiments, the compound is selected from the group consisting of Compound 21, 22, 23, 24, 25, 27, 28, 29, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 76, 82, 83, 88, 89, 90, 92, 93, 94, 95, 96, 101, 102, 103, 105, 108, 109, 111, 115, 118, 119, 120, 121, 122, 125, 126, 127, 129, 130, 131, 135, 136, 137, 138 (potential prodrug), 139, 142, 144, 145, 148, 149, and 150. These compounds have an IC50xe2x89xa62.5 xcexcM at an NMDA receptor.
In particularly preferred embodiments, the compound is selected from the group consisting of Compound 21, 22, 23, 24, 25, 27, 28, 33, 38, 39, 43, 44, 46, 47, 49, 50, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 82, 83, 89, 90, 93, 94, 95, 96, 103, 111, 118, 119, 120, 122, 126, 135, 136, 137, 138 (potential prodrug), 142, 144, 145, 148, 149, and 150. These compounds have an IC50xe2x89xa60.5 xcexcM at an NMDA receptor.
In preferred embodiments, the compound is selected from the group consisting of Compound 24, 25, 33, 50, 60, 66, 69, 103, 111, 118, 119, 120, 122, 136, 137, 138, 142, 144, 145, 148, 149, and 150.
In particularly preferred embodiments, the compound is selected from the group consisting of Compound 20, 33, 50, 60, 119, and 144.
In more particularly preferred embodiments, the compound is selected from the group consisting of Compound 33, 50, 60, 119, and 144.
In other preferred aspects, the compound is selected from the group consisting of Compound 151, 152, 153, 154, 155, 157, 158, 159, 163, 164, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 181, 185, 186, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215 and pharmaceutically acceptable salts and complexes thereof.
In other preferred aspects, the compound is selected from the group consisting of Compound 157, 158, 159, 163, 164, 166, 167, 168, 169, 170, 171, 181, 185, 186, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa610 xcexcM at an NMDA receptor.
In more preferred aspects, the compound is selected from the group consisting of Compound 157, 158, 159, 163, 164, 167, 168, 169, 170, 171, 181, 185, 186, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa62.5 xcexcM at an NMDA receptor.
In most preferred aspects, the compound is selected from the group consisting of Compound 157, 158, 159, 163, 164, 167, 168, 169, 170, 171, 181, 186, and pharmaceutically acceptable salts and complexes thereof. These compounds have an IC50xe2x89xa60.5 xcexcM at an NMDA receptor.
Excluded from the composition of matter aspect of the present invention are known compounds whose chemical structures are covered by the generic formulae presented above.
Also provided in an aspect of the invention are pharmaceutical compositions useful for treating a patient having a neurological disease or disorder. The pharmaceutical compositions are provided in a pharmaceutically acceptable carrier and appropriate dose. The pharmaceutical compositions may be in the form of pharmaceutically acceptable salts and complexes, as is known to those skilled in the art.
The pharmaceutical compositions comprise the compounds of Formulas I-IX and all preferred aspects of Formulas I-IX as set out above.
Preferred pharmaceutical compositions comprise Compounds 19-215. Preferably, the compound has an IC50xe2x89xa610 xcexcM at an NMDA receptor. More preferably the compound has an IC50xe2x89xa65 xcexcM, more preferably xe2x89xa62.5 xcexcM, and most preferably xe2x89xa60.5 xcexcM at an NMDA receptor.
In further preferred embodiments, the pharmaceutical composition comprises a compound selected from the group consisting of Compound 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 75, 76, 77, 78, 79, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 100, 101, 102, 103, 105, 106, 107, 108, 109, 111, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138 (potential prodrug), 139, 141, 142, 143, 144, 145, 146, 147, 148, 149, and 150. These compounds have an IC50xe2x89xa610 xcexcM at an NMDA receptor.
Preferably, the compound is selected from the group consisting of 21, 22, 23, 24, 25, 26, 27, 28, 29, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 76, 78, 79, 82, 83, 84, 88, 89, 90, 92, 93, 94, 95, 96, 98, 101, 102, 103, 105, 107, 108, 109, 111, 115, 116, 118, 119, 120, 121, 122, 124, 125, 126, 127, 129, 130, 131, 134, 135, 136, 137, 138 (potential prodrug), 139, 141, 142, 143, 144, 145, 148, 149, and 150.
In other embodiments, the compound is selected from the group consisting of 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 76, 82, 83, 88, 89, 90, 92, 93, 94, 95, 96, 101, 102, 103, 105, 109, 111, 115, 118, 119, 120, 121, 122, 125, 126, 127, 129, 130, 131, 135, 136, 137, 138, 139, 142, 144, 145, 148, 149, and 150.
In more preferred embodiments, the pharmaceutical composition comprises a compound selected from the group consisting of Compound 20, 21, 22, 23, 24, 25, 27, 28, 29, 30, 31, 32, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 70, 75, 76, 81, 82, 83, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 100, 101, 102, 103, 105, 106, 108, 109, 111, 115, 118, 119, 120, 121, 122, 125, 126, 127, 128, 129, 130, 131, 132, 133, 135, 136, 137, 138 (potential prodrug), 139, 142, 144, 145, 146, 148, 149, and 150. These compounds have an IC50xe2x89xa62.5 xcexcM at an NMDA receptor.
Preferably, the compound is selected from the group consisting of 21, 22, 23, 24, 25, 27, 28, 29, 33, 34, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 76, 82, 83, 88, 89, 90, 92, 93, 94, 95, 96, 101, 102, 103, 105, 108, 109, 111, 115, 118, 119, 120, 121, 122, 125, 126, 127, 129, 130, 131, 135, 136, 137, 138 (potential prodrug), 139, 142, 144, 145, 148, 149, and 150.
In particularly preferred embodiments, the pharmaceutical composition comprises a compound is selected from the group consisting of Compound 20, 21, 22, 23, 24, 25, 27, 28, 30, 31, 32, 33, 38, 39, 43, 44, 46, 47, 49, 50, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 82, 83, 89, 90, 91, 93, 94, 95, 96, 97, 103, 111, 118, 119, 120, 122, 126, 135, 136, 137, 138 (potential prodrug), 142, 144, 145, 148, 149, and 150. These compounds have an IC50xe2x89xa60.5 xcexcM at an NMDA receptor.
Preferably, the compound is selected from the group consisting of 21, 22, 23, 24, 25, 27, 28, 33, 38, 39, 43, 44, 46, 47, 49, 50, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 69, 82, 83, 89, 90, 93, 94, 95, 96, 103, 111, 118, 119, 120, 122, 126, 135, 136, 137, 138 (potential prodrug), 142, 144, 145, 148, 149, and 150.
In more preferred embodiments, the pharmaceutical composition comprises a compound selected from the group consisting of Compound 20, 24, 25, 33, 50, 60, 66, 69, 103, 111, 118, 119, 120, 122, 136, 137, 138, 142, 144, 145, 148, 149, and 150.
Preferably, the compound is selected from the group consisting of Compound 24, 25, 33, 50, 60, 66, 69, 103, 111, 118, 119, 120, 122, 136, 137, 138, 142, 144, 145, 148, 149, and 150.
In most particularly preferred embodiments, the pharmaceutical composition comprises a compound selected from the group consisting of Compound 20, 33, 50, 60, 119, and 144.
Preferably, the compound is selected from the group consisting of 33, 50, 60, 119, and 144.
In other preferred aspects, the pharmaceutical composition comprises a compound selected from the group consisting of compound 151, 152, 153, 154, 155, 157, 158, 159, 163, 164, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 181, 185, 186, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215 and pharmaceutically acceptable salts and complexes thereof, and a pharmaceutically acceptable carrier.
In other preferred aspects the pharmaceutical composition comprises a compound which is selected from the group consisting of Compound 157, 158, 159, 163, 164, 166, 167, 168, 169, 170, 171, 181, 185, 186, and pharmaceutically acceptable salts and complexes thereof, and a pharmaceutically acceptable carrier. These compounds have an IC50xe2x89xa610 xcexcM at an NMDA receptor.
In more preferred aspects, the pharmaceutical composition comprises a compound which is selected from the group consisting of Compound 157, 158, 159, 163, 164, 166, 167, 168, 169, 170, 171, 181, 185, 186, and pharmaceutically acceptable salts and complexes thereof, and a pharmaceutically acceptable carrier. These compounds have an IC50xe2x89xa62.5 xcexcM at an NMDA receptor.
In most preferred aspects, the pharmaceutical composition comprises a compound which is selected from the group consisting of Compound 157, 158, 159, 163, 164, 167, 168, 169, 170, 171, 181, 186, and pharmaceutically acceptable salts and complexes thereof, and a pharmaceutically acceptable carrier. These compounds have an IC50xe2x89xa60.5 xcexcM at an NMDA receptor.
Structural modifications can be made to compounds such as 20 or 60 which do not add materially to the structure-activity relationships (SAR) illustrated here. For example, successful bioisosteric replacement or substitution of optionally substituted phenyl groups, such as those occurring in Compounds 20 or 60, can be accomplished with other lipophilic or semi-polar aromatic (e.g., naphthyl, naphthoxy, benzyl, phenoxy, phenylthio), aliphatic (alkyl, e.g., isopropyl), cycloaliphatic (cycloalkyl, e.g., cyclohexyl), heterocyclic [e.g., pyridyl, furanyl, thiofuranyl (thiophenyl)], or other functional groups or systems, as is well known in the art, will afford clinically useful compounds (structural homologs, analogs, and/or congeners) with similar biopharmaceutical properties and activity at the NMDA receptor (e.g., cf. Compounds 37, 75, 79, 83, 89, 119-122, 125, 126, 128, 130, 132, 137, 144, and 145). For example, such replacements or substitutions have been used to great effect in the development of SAR among other groups of highly clinically and commercially successful synthetic pharmaceutical agents such as the classical H1-antihistamines, anticholinergics (antimuscarinics; e.g., anti-Parkinsonians), antidepressants (including tricyclic compounds), and opioid analgesics [See, Foye et al. (Eds.), Principles of Medicinal Chemistry, 4th ed., Lea and Febiger/Williams and Wilkins, Philadelphia, Pa., 1995, pp. 233, 265, 281-282, 340-341, 418-427, and 430; Prous, J. R., The Year""s Drug News, Therapeutic Targetsxe2x80x941995 Edition, Prous Science Publishers, Barcelona, Spain, 1995, pp. 13, 55-56, 58-59, 74, 89, 144-145, 152, 296-297, and 317]. Similarly, bioisosteric replacement or substitution of the methylene or methine groups in the propyl backbone of compounds such as 20 or 60 with, e.g., oxygen, sulfur, or nitrogen, will afford clinically useful NMDA receptor-active compounds with similarly useful biopharmaceutical properties, such as Compound 88 (a modified xe2x80x9cclassical H1-antihistamine-typexe2x80x9d structure), which can be further optimized for activity at the NMDA receptor by preparing, e.g., the corresponding compound(s) containing, e.g., (bis)(3-fluorophenyl) group(s), as taught by the present invention. The propyl backbone of compounds such as 20 and 60 may also be modified successfully by the incorporation of ring systems (as in Compounds 102 and 111) and/or unsaturation (e.g., a double bond, as in Compounds 81, 106, 109, and 139) to afford further clinically useful NMDA receptor-active compounds of the present invention (cf. compounds cited above).
In a related aspect, the invention features a method for making a therapeutic agent comprising the steps of screening for said agent by determining whether said agent is active on a receptor-operated calcium channel, and synthesizing said therapeutic agent in an amount sufficient to provide said agent in a therapeutically effective amount to a patient. Said screening may be performed by methods known to those of ordinary skill in the art, and may, for example be performed by the methods set out herein. Those skilled in the art are also familiar with methods used to synthesize therapeutic agents in amounts sufficient to be provided in a therapeutically effective amount.
In a preferred aspect, said receptor-operated calcium channel is an NMDA receptor. In a more preferred aspect, said method further comprises the step of adding a pharmaceutically acceptable carrier to said agent. In a further preferred aspect said therapeutic agent comprises a compound of Formula I, as set out herein. In a further preferred aspect said therapeutic agent comprises a compound of Formula II, III, IV, V, VI, VII, VIII, or IX, as set out herein. In particularly preferred aspects, said therapeutic agent comprises a compound having a structure selected from the group consisting of Formulas I-IX, and all preferred aspects of said formulas as set out herein. In further preferred aspects, said therapeutic agent is selected from the group consisting of Compounds 19-215. In a particularly preferred aspect, said therapeutic agent is provided to a patient having a neurological disease or disorder. In a related aspect, said screening comprises the step of identifying a compound which binds to said receptor-operated calcium channel at a site bound by one of the arylalkylamines Compound 1, Compound 2, and Compound 3. 
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.
The following is a detailed description of the methods and tests by which therapeutically useful compounds can be identified and utilized for the treatment of neurological disorders and diseases. The tests are exemplified by use of Compound 1, Compound 2 or Compound 3, but other compounds which have similar biological activity in these assays can also be used (as discovered) to improve on the tests. Lead compounds such as Compound 1, Compound 2 or Compound 3 can be used for molecular modeling using standard procedures, or existing or novel compounds in natural product libraries can be screened by the methods described below.
One key method is the means by which compounds is can be quickly screened with standard radioligand binding techniques (a radiolabeled arylalkylamine binding assay) to identify those which bind at the same site on receptor-operated Ca2+ channels as Compound 1, Compound 2 or Compound 3. Data from such radioligand binding studies will also confirm that said compounds do not inhibit [3H]arylalkylamine binding via an action at the known sites on receptor-operated Ca2+ channels (such as the glutamate binding site, glycine binding site, MK-801 binding site, Zn2+ binding site, Mg2+ binding site, sigma binding site, or polyamine binding site on the NMDA receptor-ionophore complex). This screening test allows vast numbers of potentially useful compounds to be identified and screened for activity in the other assays. Those skilled in the art will recognize that other rapid assays for detection of binding to the arylalkylamine site on receptor-operated Ca2+ channels can be devised and used in this invention.
Additional testing utilizes electrophysiological (patch clamp) methodology to extend the results obtained with the above-mentioned radioligand binding assay. Such results will confirm that compounds binding to the arylalkylamine site are functional, noncompetitive antagonists of receptor-operated Ca2+ channels with the following properties in common with the arylalkylamines themselves: open-channel block manifested as use-dependent block, and voltage-dependent onset and reversal from block. Such results will also confirm that said compounds do not have their primary activity at the previously described sites on receptor-operated Ca2+ channels (such as the glutamate binding site, glycine binding site, MK-801 binding site, Zn2+ binding site, Mg2+ binding site, sigma binding site, or polyamine binding site on the NMDA receptor-ionophore complex).
In addition, recombinant DNA technology can be used to make such testing even more rapid. For example, using standard procedures, the gene(s) encoding the novel arylalkylamine binding site (i.e., receptor) can be identified and cloned. This can be accomplished in one of several ways. For example, an arylalkylamine affinity column can be prepared, and solubilized membranes from cells or tissues containing the arylalkylamine receptor passed over the column. The receptor molecules bind to the column and are thus isolated. Partial amino acid sequence information is then obtained which allows for the isolation of the gene encoding the receptor. Alternatively, cDNA expression libraries are prepared and subfractions of the library are tested for their ability to impart arylalkylamine receptors on cells which do not normally express such receptors (e.g., CHO cells, mouse L cells, HEK 293 cells, or Xenopus oocytes). In this way, the library fraction containing the clone encoding the receptor is identified. Sequential subfractionation of active library fractions and assay eventually results in a single clone encoding the arylalkylamine receptor. Similarly, hybrid-arrest or hybrid-depletion cloning can be used. Xenopus oocytes are injected with mRNA from an appropriate tissue or cell source (e.g., human brain tissue). Expression of the arylalkylamine receptor is detected as, for example, an NMDA- or glutamate-stimulated influx of calcium which can be blocked by Compound 1, Compound 2 or Compound 3. cDNA clones are tested for their ability to block expression of this receptor when cDNA or cRNA are hybridized to the mRNA of choice, prior to injection into Xenopus oocytes. The clone responsible for this effect is then isolated by the process described above. Once the receptor gene is isolated, standard techniques are used to identify the polypeptide or portion(s) thereof which is (are) sufficient for binding arylalkylamines (the arylalkylamine binding domain[s]). Further, using standard procedures, the entire receptor or arylalkylamine binding domain(s) can be expressed by recombinant technology. Said receptor or binding domain(s) can be isolated and used as a biochemical reagent such that, rather than using a competitive assay exemplified below, a simple direct binding assay can be used. That is, a screen is set up for compounds which bind at the novel arylalkylamine receptor. In this way large numbers of compounds can be simultaneously screened, e.g., by passage through a column containing the novel arylalkylamine receptor or arylalkylamine binding domain, and analysis performed on compounds which bind to the column.
Additional testing utilizes the combination of molecular biological techniques (expression of cloned NMDA, AMPA or nicotinic cholinergic receptors) and patch clamp electrophysiological techniques. Specifically, arylalkyl-amine analogs can be rapidly screened for potency at cloned and expressed subunits of the above-mentioned receptor-ionophore complexes. Site-directed mutagenesis can be utilized in an effort to identify which amino acid residues may be important in determining arylalkylamine potency.
Desired properties of a drug include: high affinity and selectivity for receptor-operated Ca2+ channels, such as those present in NMDA, AMPA and nicotinic cholinergic receptor-ionophore complexes (compared to responses mediated via other neurotransmitter receptors, neurotransmitter receptor-operated ion channels, or voltage-dependent ion channels) and a noncompetitive antagonism of said receptor-operated Ca2+ channels.
The NMDA receptor-ionophore complex is utilized as an example of a receptor-operated Ca2+ channel. Activation of the NMDA receptor opens a cation-selective channel that allows the influx of extracellular Ca2+ and Na+, resulting in increases in [Ca2+]i and depolarization of the cell membrane. Measurements of [Ca2+]i were used as primary assays for detecting the activity of arylalkylamine compounds on NMDA receptors. Purified arylalkylamines, synthetic aryl-alkylamines, and synthetic analogs of arylalkylamines were examined for activity in in vitro assays capable of measuring glutamate receptor activity. Selected for detailed study were the arylalkylamines present in the venom of various spider species. The arylalkylamines present in these venoms are structurally distinct but have the basic structure of the class represented by Compounds 1 through 3. Other more simplified synthetic analogs generally consist of suitably substituted aromatic chromophoric groups attached to an alkyl(poly)amine moiety (see Compounds 19 through 215 below).
A primary assay that provides a functional index of glutamate receptor activity and that allows high-throughput screening was developed. Primary cultures of rat cerebellar granule cells loaded with the fluorimetric indicator fura-2 were used to measure changes in [Ca2+]i elicited by NMDA and its coagonist glycine. This assay provides an extremely sensitive and precise index of NMDA receptor activity. Increases in [Ca2+]i evoked by NMDA are dependent on the presence of glycine, and are blocked by extracellular Mg2+ or antagonists acting at the glutamate, glycine, or MK-801 binding sites. Increases in [Ca2+]i elicited by NMDA/glycine are readily distinguished from those resulting from depolarization by their refractoriness to inhibition by blockers of voltage-sensitive Ca2+ channels. The fidelity with which measurements of [Ca2+]i corroborate results obtained by electrophysiological and ligand-binding studies suggests that such measurements mirror closely activation of the NMDA receptor-ionophore complex.